How should I use both Show and Hide actions on the same element?

I have a button which I want to show if the logged in user has the right permission. I also want to hide it if a variable has a particular value. But, the Show action seems to take priority and shows the button because of the logged in status despite me wanting to hide it.

So, what’s the technique for combining the two conditions into the same action? eg. Show if logged in user has permission AND variable is not set.

Cheers, Jon.